Circuit interrupter

ABSTRACT

A circuit interrupter comprises a trip plate including a stop for limiting the stroke of a movable contact arm. Upon an excessive current flow the interrupter a bimetal and/or an electromagnet causes the trip plate to be moved in such a direction that the movable contact is separated from the stationary contact by a distance greater than that provided by the normal opening operation.

United States Patent Inventors Appl. No. Filed Patented AssigneePriority CIRCUIT INTERRUPTER 1 Claim, 2 Drawing Figs.

Primary Examiner-Harold Broome A!t0rney-Wenderoth, Lind & PonackABSTRACT: A circuit interrupter comprises a trip plate including a stopfor limiting the stroke of a movable contact arm.

US. Cl 335/43, Upon an excessive current flow the interrupter a bimetal335/174 and/or an electromagnet causes the trip plate to be moved inInt. Cl ..II0lh 73/48 such a direction that the movable contact isseparated from Field of Search 335/14, 15, the stationary contact by adistance greater than that provided 16,43, 173, 174; 200/169 by thenormal opening operation.

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\ INVENTORS WASABURO MURAI l KIYOSHI HIROI mwzz wm ATTORNEYS CIRCUITINTERRUPTER This invention relates to improvements in a circuitinterrupter.

In order to effectively interrupt the overload or short-circuitingcurrent flowing through circuit interrupters, it is desirable to providea relatively great distance between a pair of separated contactsinvolved. This measure is objectionable in the case where theinterrupters have to be manually operated. This is because making thedistance between the separatedcontacts greater leads to difficulties indesign and construction and the durability decreases.

Accordingly, an object of the invention is to provide a circuit breakercapable of changing the separation distance between the contacts from asmall magnitude for manual opening operation to a large magnitude forautomatic opening operation and wherein there is provided an improvedmechanism by which the operation is rapidly and smoothly performed.

The invention accomplishes this object by the provision of a circuitinterrupter comprising in combination, a pair of relatively movablecontacts, an arm having disposed thereon one of said contacts, aswitching mechanism coupled to said movable contact arm for driving saidmovable contact from its closed position to its open position and viceversa, a trip plate operative to automatically release said movablecontact arm to separate said movable contact away from the other contactand a stop disposed on said trip plate to limit the separation movementof said movable contact arm from the other contact, the arrangementbeing such that upon automatically releasing the movable contact arm,said stopper is moved in a direction to increase the spacing betweensaid pair of contacts as compared with the spacing between the contactsprovided through the manual operation of the operating mechanism.

The invention will become more readily apparent from the followingdescription taken in conjunction with the accompanying drawing in which:

FIG. 1 is a side elevational view partly in section of a circuitinterrupter in its closed position constructed in accordance with theteachings of the invention; and

FIG. 2 is a schematic side elevational view of one portion of thecircuit interrupter illustrated in FIG. 1 useful in explaining theoperation of the invention.

While the invention will be shown and described in conjunction with acircuit interrupter of the three pole type, it is to be understood thatthe same is equally applicable to circuit interrupters of the singlepole type and other multiple pole types. Also it is to be understoodthat the components common to all the poles will be described in termsof the central pole alone.

Referring now to the drawings and more particularly to FIG. 1, there isillustrated a three-pole circuit interrupter constructed in accordancewith the teachings of the invention. The arrangement illustratedcomprises a base member 2 and a detachable cover member 4 forming aclosed enclosure. Both the members may be conveniently made of anysuitable electrically insulating plastic by a moulding technique.Disposed at the bottom of the enclosure is a stationary contact 6connected by way of an electric conductor 8 to a source terminal 10. Amovable contact arm 12 of any suitable electrically conductive materialis provided at that end facing the stationary contact 6 with a movablecontact 14 and is rotatably secured by a pin 16 to a contact holder 18pivotally mounted on an electrically insulating shaft 20 common to allthe poles. The movable contact arm 12 is always biased toward thestationary contact 6 by the action of a spring 21 disposed around thepin 16 and is connected to a connector 22 through a flexible conductor24.

In order to move the movable contact arm 12 from its closed position asillustrated in FIG. 1 to its open position as illustrated at solid linein FIG. 2 and vice versa, an operating mechanism generally designated bythe reference numeral 26 is provided including an operating handle 28,an operating lever 30, operating springs 32 and a trip plate 34. Theoperating handle 28 is made of any suitable electrically insulatingmaterial and is fixedly mounted on one end of the operating lever 30with the other end portion projecting beyond the cover member 4. Theoperating lever 30 is of an inverted U- shape section and is pivotablymounted at the other end on a pin 36 secured to a stationary frame 38.The operating springs 32 are anchored at one end to the one end portionof the lever 30 and are rotatably mounted on a toggle shaft 40. The tripplate 34 is in the form of a bell crank including one arm pivotablymounted on the frame 38 by a pivot pin 42. When the movable contact arm12 is in its manually open position as will be described hereinafter thetrip plate 34 is adapted to be contacted at the free end 34a by thecontact arm 12 thereby to prevent the arm from effecting a furthermovement in a direction to separate the movable contact 14 from thestationary contact 6. The trip plate 34 is further provided on themiddle portion with a toggle pin 44.

A toggle link 46 is pivotably mounted at one end on the toggle pin 44and articulated at the other end to another toggle link 48 by the toggleshaft 40. The toggle link 48 has its free end connected to the pin 16along with the contact holder 18 and movable contact arm 12.

As shown in FIG. 1, the trip plate 34 normally engages a trip hook 50.More specifically, the trip hook 50 is rotatably supported on thestationary frame 38 by a pin 52 secured to the latter and includes aflat section generally upwardly directed and is provided on the upperend portion with a slot 54 which, in turn, normally engages the free end341) of the other arm of the trip plate 34.

A trip shaft 56 common to all the poles is rotatably supported by thestationary frame 38 and adjacent the trip hook 50. The shaft has fixedlysecured thereon a protrusion 58 normally engaging the trip hook 50,under the action of a spring 60 disposed around the pin 52. The shaft 56has further fixed thereon one trip piece 62 for each pole.

The arrangement further comprises an electromagnetically and thermallyresponsive device generally designated by the reference numeral 64. Thedevice 64 includes a stationary electromagnet 66 having a cylindricalportion 66a around which a conductor 68 is wound. The conductor 68 hasone end connected to the flexible conductor 24 through the connector 22and the other end connected to one end of heater 70. The heater 70 hasthe other end connected to a conductor 72 connected to a load terminal74. An L-shaped bimetal element 76 is disposed in close proximity to theheater 70 by having the lower shorter leg of the L mechanicallyconnected to the adjacent portion of the heater 70 and there iscontrollably screw threaded into the upper end of the other leg anadjusting screw 78 facing both the free end of the trip piece 62 and oneend of a movable iron piece 80. The movable iron piece 80 is rotatablysecured at a point intermediate the two ends to the stationary frame 38by a pin 82 and has the other end portion opposed to the stationaryelectromagnet 66. A spring 84 engages the pin 82 to normally maintainthe movable iron piece 80 spaced away from the electromagnet 66. Underthese circumstance, the one end of the iron piece 80 is slightly spacedaway from the end of the adjusting screw 78.

Further an arc-extinguishing space 86 having a conventional constructionis disposed in the region of the movable contact arm 14 as shown in FIG.1.

In order to manually move the interrupter from its closed position asillustrated in FIG. 1 to its open position, the operating handle 28 canbe turned to the OFF side or in the righthand direction as viewed inFIG. 1. This turning movement of the operating handle 28 causes the pairof toggle links 46 and 48 to be folded into a V-shape due to thereversal of the line of action of the operating springs 32 which pull upthe pin 16 on the movable contact arm 12. Therefore the movable contactarm 12 is rotated about the axis of the shaft 20 in the clockwisedirection as viewed in FIG. 1 until it abuts against the lower end 34aof the trip plate 34 whereupon the arm is stopped at its position asshown at solid line in FIG. 2, resulting in the completion of theparticular manual opening operation. As shown in FIG. 2, the movablecontact 14 is maintained spaced away from the surface of the stationarycontact 6 by a minimum distance L,,. It is easily understood that amanual closing operation can be accomplished by turning the operatinghandle 28 in the left-hand direction as viewed in FIG. 1.

Upon the occurrence of a flow of overload current through theinterrupter in its closed position, the bimetal element 76 isexcessively heated and is deflected so that the free end thereof pushesthe trip piece 62. This causes the trip shaft 56 and therefore itsprotrusion 58 to be rotated in the counterclockwise direction as viewedin FIG. 1 against the action of the spring 60 until the protrusion fallsinto the slot 54 on the trip hook 50. At that time the end 34b of thetrip plate 34 disengages from the trip hook 50 to permit that plate tobe rotated in a counterclockwise direction by the action of theoperating spring 32 through the toggle link 46. This rotational movementof the trip plate 34 causes the toggle links 46 and 48 to collapseresulting from the reversal of the line of action of the spring 32thereby to pull up the contact holder until the interrupter is in itsopen position.

If an excessive current whose magnitude may be on the order of 5 to l0times the rating current flows through interrupter in its closedposition then the movable iron piece 80 is attracted by the energizedelectromagnet so as to be rotated about the axis of the pin 82 in thecounterclockwise direction and against the action of the spring 84 untilit pushes the trip piece 62. Thereafter the process as above describedis carried out to separate the movable contact 14 from the stationarycontact 6.

After the tripping operation has been performed the movable contact ann12 is located at the position as shown by dotand-dash lines in FIG. 2.It is to be noted that with the tripping operation the movable contact12 has been separated from the surface of the stationary contact 6 by amaximum distance L greater than the minimum distance of L obtained withthe manual opening for the following reason:

As clearly shown by dot-and-dash lines in FIG. 2, the counterclockwiserotation of the tripping plate 34 results also in the upward movement ofthe protrusion 34a. Therefore, the movable contact arm 12 is permittedto be additionally moved beyond its open position provided by the manualopening operation until it abuts against the upwardly moved protrusion34a for stopping. Thus the separation between the movable and stationarycontacts is greater in the tripping operation than in the manual openingoperation.

In summary, the operating handle 28 is manually operated to separate themovable contact 14 from the stationary contact 6 a relatively smalldistance L In a tripping operation due to the occurrence of a flow ofover load or shortcircuiting current, the lower end of the.bellcrank-shaped trip plate 34 is moved to permit the movable contact14 to be moved away from the stationary contact 6 a distance greaterthan that obtained in the manual operation of the handle 28. Thereforethe invention is advantageous in that for the normal switchingoperation, damage to the flexible conductor 24 and chattering of themovable contact arm 12 greatly decreases leading to an increase indurability because a relatively small separation distance permits thereasonable construction of circuit interrupters. At the same time, arelatively long separation distance obtained in a tripping operation oran automatic interrupting operation which results in an increase ininterrupting capability.

While the invention has been illustrated and described in conjunctionwith a single preferred embodiment thereof it is to be understood thatvarious changes and modification in the details of construction and thecombination and arrangement of parts may be resorted to withoutdeparting from the spirit and scope of the invention. Instead of thestationary contact 6, a movable or semimovable contact may be used, ifdesired.

What we claim is:

l. A circuit interrupter comprising in combination a pair of relativelymovable contacts, a movable contact arm having dispose thereon one ofsaid contacts, a switching mechanism coupled to said movable contact armfor driving said movable contact from a closed position to an openposition and vice versa, a trip plate pivotally mounted on saidswitching mechanism, a pair of foldable toggle links pivotably coupledat one end to the contact arm and at the other end to said trip plate,said trip plate normally being held in a first position and operative tobe pivoted to a second position to actuate said toggle links andautomatically actuate said switching mechanism to move said movablecontact arm to separate said movable contact from the other contact uponflow of an excessive current, and a stop on said trip plate adjacent thepivotal mounting of said trip plate to limit the movement of saidmovable contact arm away from the other contact, the stop being in aposition when the trip plate is in the second position which increasesthe distance the movable contact moves away from the other contact ascompared with the distance the movable contact arm can move with thetrip plate in said first position so as to increase the spacing betweenthe contacts upon automatic operation as compared with manual operation.

1. A circuit interrupter comprising in combination a pair of relativelymovable contacts, a movable contact arm having disposed thereon one ofsaid contacts, a switching mechanism coupled to said movable contact armfor driving said movable contact from a closed position to an openposition and vice versa, a trip plate pivotally mounted on saidswitching mechanism, a pair of foldable toggle links pivotably coupledat one end to the contact arm and at the other end to said trip plate,said trip plate normally being held in a first position and operative tobe pivoted to a second position to actuate said toggle links andautomatically actuate said switching mechanism to move said movablecontact arm to separate said movable contact from the other contact uponflow of an excessive current, and a stop on said trip plate adjacent thepivotal mounting of said trip plate to limit the movement of saidmovable contact arm away from the other contact, the stop being in aposition when the trip plate is in the second position which increasesthe distance the movable contact moves away from the other contact ascompared with the distance the movable contact arm can move with thetrip plate in said first position so as to increase the spacing betweenthe contacts upon automatic operation as compared with manual operation.